1. Field of the Invention
The present invention relates to an etching process. More particularly, the present invention relates to an etching process that includes a step of removing the polymer generated in the etching step of the bottom anti-reflection coating (BARC), and relates to a patterning process including the etching process.
2. Description of the Related Art
As the IC industry advances rapidly, the dimension of devices is continuously reduced to make higher and higher integration degree. When the process linewidth is down to less than 0.13 μm, the KrF-248 nm lithography techniques are no more suitable, and ArF-193 nm lithography techniques are used instead. However, since light having a shorter wavelength has higher reflectivity at the interface of the photoresist layer and the die, the resulting photoresist patterns are distorted more easily. The problem is even more significant when a layer of high-reflectivity material, such as, polysilicon or metal like aluminum, is to be patterned, since the degree of pattern distortion increases with the intensity of the reflective light. Accordingly, when the process linewidth is small and the reflectivity of the film to be patterned is high, controlling the critical dimension is particularly difficult.
Conventionally, the issue of reflective light is solved by forming a bottom anti-reflection coating (BARC) on the material layer to be etched prior to the photoresist layer. After the photoresist layer is patterned with a lithography method, the BARC is etched/patterned using the patterned photoresist layer as a mask. Then, the material layer is etched using the patterned photoresist layer as a mask, so that the photoresist patterns are transferred to the material layer.
However, during the etching step of the BARC, polymer as an etching by-product is usually deposited on the patterned photoresist layer, so that the photoresist patterns are changed and the pattern linewidth is increased. Therefore, in the latter step of etching the material layer, the patterns transferred to the material layer and the critical dimension thereof are not correct.